CVE-2026-68179
HighCVSS 8.4Exploitation Probability (EPSS)
Low risk8th percentile - higher than 8% of all known CVEs
Summary
In the Linux kernel, the NSM misc driver's nsm_dev_ioctl() can unlock a mutex that was never locked when copy_from_user fails before acquiring the lock, leading to a bad unlock balance warning. The fix returns immediately on pre-lock failure.
Risk Assessment
The risk includes improper driver behavior, potential system crashes, or unpredictable behavior due to incorrect synchronization.
Recommendation
Apply the Linux kernel patch that fixes the error path in the NSM driver.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: misc: nsm: only unlock nsm_dev on post-lock error paths nsm_dev_ioctl() jumps to the common out label even when the initial copy_from_user() fails before nsm->lock has been taken. The error path then blindly unlocks a mutex that was never acquired. This issue was found by our static analysis tool and then manually reviewed against the current tree. The grounded PoC kept the miscdevice ioctl entry and the pre-lock copy_from_user(&raw, argp, _IOC_SIZE(cmd)) failure path by issuing NSM_IOCTL_RAW with an invalid user pointer. That failure reaches the shared out label before mutex_lock(&nsm->lock). Lockdep reported: WARNING: bad unlock balance detected! exploit/193 is trying to release lock (&global_nsm.lock) at: nsm_dev_ioctl+0x5f/0xcf [vuln_msv] but there are no more locks to release! no locks held by exploit/193. Return immediately on the pre-lock copy_from_user() failure and keep the common unlock label for the post-lock paths only.